Heretofore, as a circuit assembly for distributing a power from a common power supply to a plurality of loads in a vehicle such as an automobile, there has been generally known an electric connection box including a bus bar board. The bus bar board is of a laminated construction with alternating bus bar layers serving as a power circuit and insulating plates. From each of the bus bar layers are perpendicularly bent a plurality of tab terminals, to which circuit-protective fuse elements and switching elements such as a relay switch are connected.
Late years, there has also been known a power distributor intended to reduce a thickness of the circuit assembly, as disclosed in the following Patent Publication 1. In this power distributor, a switching element consisting of a FET or the like is interposed between a power-input bus bar and each of a plurality of output bus bars. Each of the output bus bars is divided into two segments at an intermediate position thereof, and a fuse member is welded to the segments so as to bridge therebetween. According to this power distributor, a thickness of the entire circuit assembly can be reduced. Further, even if the switching element fails to be turned off during occurrence of an overcurrent, a circuit and a vehicle-mounted load on a downstream side of the fuse member is protected from the overcurrent since the fuse member in the output bus bar associated with the failed switching element is fused.
Patent Publication 1: Japanese Patent Laid-Open Publication No. 2001-286037
In the aforementioned structure where the fuse element is attached to each of the tab terminals perpendicularly bent from the bus bar board in place, the fuse elements are scattered on the bus bar board, which is liable to cause structural complexity, and difficulty in concentrated management of the fuse elements in one place.
In the power distributor disclosed in the Patent Publication 1, the fuse member cannot be replaced with a new one when burned out, because the fuse member is welded to be integrally incorporated in each of the output bus bars of the power distributor. Consequently, the application of this fuse member is liable to be limited to a region with extremely low possibility of meltdown, like a region where a fail-safe fuse for the occasion when a switching element such as a FET fails to be turned off in spite of occurrence of overcurrent is set.